Pump assembly for a dishwashing appliance

ABSTRACT

A dishwasher appliance includes a sump housing defining a sump for collecting wash fluid, the sump defining a recirculation chamber, a soil collection chamber, and a rotor housing positioned between the recirculation chamber and the soil collection chamber. A rotor assembly is positioned in the rotor housing and includes a concentric central hub and annular rotor magnet spaced apart to define a flow path between the recirculation chamber and the soil collection chamber. A plurality of helical vanes extend between the central hub and the annular rotor magnet and the annular rotor magnet is selectively rotated by a stator assembly positioned around the rotor housing outside of the sump.

FIELD OF THE INVENTION

The present disclosure relates generally to dishwasher appliances, and more particularly to improved pump assemblies for dishwasher appliances.

BACKGROUND OF THE INVENTION

Dishwasher appliances generally include a tub that defines a wash chamber. Wash fluid (e.g., various combinations of water and detergent along with optional additives) may be introduced into the tub where it collects in a sump space at the bottom of the wash chamber. Rack assemblies can be mounted within the wash chamber for receipt of articles for washing and multiple spray assemblies may be configured for directing the wash fluid towards articles disposed within the rack assemblies in order to clean such articles. During wash and rinse cycles, a circulation pump may be used to pump the wash fluid to the multiple spray assemblies and a device referred to as a diverter may be used to control the flow of wash fluid received from the pump.

Conventional circulation pumps are motor driven and positioned outside of the wash chamber in a horizontal orientation. Notably, this positioning requires that one or more seals be used to connect the pump inlet and outlet to the wash chamber, thereby increasing the likelihood of leaks. Certain circulation pumps are positioned within the sump but may require complex constructions to ensure safe operation of the electric motor in the wet environment. In addition, certain constructions utilize a rotor positioned within the sump, but often require additional hoses, conduits, or seals to facilitate a draining operation.

Accordingly, a dishwasher appliance that utilizes an improved fluid distribution system or pump assembly would be useful. More specifically, a pump assembly that is compact and facilitates wash and drain cycles with minimal potential for leaks would be particularly beneficial.

BRIEF DESCRIPTION OF THE INVENTION

Aspects and advantages of the invention will be set forth in part in the following description, or may be obvious from the description, or may be learned through practice of the invention.

In one exemplary aspect of the present disclosure, a dishwasher appliance defining a vertical direction is provided. The dishwasher appliance includes a wash tub that defines a wash chamber and a sump housing defining a sump for collecting wash fluid, the sump defining a recirculation chamber, a soil collection chamber, and a rotor housing positioned between the recirculation chamber and the soil collection chamber. A rotor assembly is rotatably mounted within the rotor housing and a stator assembly is positioned around the rotor housing outside of the sump for selectively rotating the rotor assembly.

In another exemplary aspect of the present disclosure, a pump assembly for a dishwashing appliance is provided. The dishwashing appliance includes a sump housing defining a sump for collecting wash fluid, the sump defining a recirculation chamber, a soil collection chamber, and a rotor housing positioned between the recirculation chamber and the soil collection chamber. The pump assembly includes a drive shaft defining an axial direction and a radial direction perpendicular to the axial direction, a rotor assembly coupled to the drive shaft and being rotatably mounted within the rotor housing, and a stator assembly positioned around the rotor housing outside of the sump for selectively rotating the rotor assembly.

These and other features, aspects and advantages of the present invention will become better understood with reference to the following description and appended claims. The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments of the invention and, together with the description, serve to explain the principles of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

A full and enabling disclosure of the present invention, including the best mode thereof, directed to one of ordinary skill in the art, is set forth in the specification, which makes reference to the appended figures.

FIG. 1 provides a perspective view of an exemplary embodiment of a dishwashing appliance of the present disclosure with a door in a partially open position.

FIG. 2 provides a side, cross sectional view of the exemplary dishwashing appliance of FIG. 1.

FIG. 3 provides a cross sectional view of a pump assembly that may be positioned within a sump of the exemplary dishwashing appliance of FIG. 1 according to an exemplary embodiment of the present subject matter.

FIG. 4 provides a perspective view of a rotor assembly of the exemplary pump assembly of FIG. 3 according to an example embodiment of the present subject matter, with an annular rotor magnet removed for clarity.

Repeat use of reference characters in the present specification and drawings is intended to represent the same or analogous features or elements of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Reference now will be made in detail to embodiments of the invention, one or more examples of which are illustrated in the drawings. Each example is provided by way of explanation of the invention, not limitation of the invention. In fact, it will be apparent to those skilled in the art that various modifications and variations can be made in the present invention without departing from the scope or spirit of the invention. For instance, features illustrated or described as part of one embodiment can be used with another embodiment to yield a still further embodiment. Thus, it is intended that the present invention covers such modifications and variations as come within the scope of the appended claims and their equivalents.

As used herein, the term “article” may refer to, but need not be limited to dishes, pots, pans, silverware, and other cooking utensils and items that can be cleaned in a dishwashing appliance. The term “wash cycle” is intended to refer to one or more periods of time during which a dishwashing appliance operates while containing the articles to be washed and uses a detergent and water, preferably with agitation, to e.g., remove soil particles including food and other undesirable elements from the articles. The term “rinse cycle” is intended to refer to one or more periods of time during which the dishwashing appliance operates to remove residual soil, detergents, and other undesirable elements that were retained by the articles after completion of the wash cycle. The term “drain cycle” is intended to refer to one or more periods of time during which the dishwashing appliance operates to discharge soiled water from the dishwashing appliance. The term “wash fluid” refers to a liquid used for washing and/or rinsing the articles and is typically made up of water that may include other additives such as detergent or other treatments. Furthermore, as used herein, terms of approximation, such as “approximately,” “substantially,” or “about,” refer to being within a ten percent margin of error.

FIGS. 1 and 2 depict an exemplary domestic dishwasher or dishwashing appliance 100 that may be configured in accordance with aspects of the present disclosure. For the particular embodiment of FIGS. 1 and 2, the dishwasher 100 includes a cabinet 102 having a tub 104 therein that defines a wash chamber 106. As shown in FIG. 2, tub 104 extends between a top 107 and a bottom 108 along a vertical direction V, between a pair of side walls 110 along a lateral direction L, and between a front side 111 and a rear side 112 along a transverse direction T. Each of the vertical direction V, lateral direction L, and transverse direction T are mutually perpendicular to one another.

The tub 104 includes a front opening 114 and a door 116 hinged at its bottom for movement between a normally closed vertical position (shown in FIG. 2), wherein the wash chamber 106 is sealed shut for washing operation, and a horizontal open position for loading and unloading of articles from the dishwasher 100. According to exemplary embodiments, dishwasher 100 further includes a door closure mechanism or assembly 118 that is used to lock and unlock door 116 for accessing and sealing wash chamber 106.

As best illustrated in FIG. 2, tub side walls 110 accommodate a plurality of rack assemblies. More specifically, guide rails 120 may be mounted to side walls 110 for supporting a lower rack assembly 122, a middle rack assembly 124, and an upper rack assembly 126. As illustrated, upper rack assembly 126 is positioned at a top portion of wash chamber 106 above middle rack assembly 124, which is positioned above lower rack assembly 122 along the vertical direction V. Each rack assembly 122, 124, 126 is adapted for movement between an extended loading position (not shown) in which the rack is substantially positioned outside the wash chamber 106, and a retracted position (shown in FIGS. 1 and 2) in which the rack is located inside the wash chamber 106. This is facilitated, for example, by rollers 128 mounted onto rack assemblies 122, 124, 126, respectively. Although a guide rails 120 and rollers 128 are illustrated herein as facilitating movement of the respective rack assemblies 122, 124, 126, it should be appreciated that any suitable sliding mechanism or member may be used according to alternative embodiments.

Some or all of the rack assemblies 122, 124, 126 are fabricated into lattice structures including a plurality of wires or elongated members 130 (for clarity of illustration, not all elongated members making up rack assemblies 122, 124, 126 are shown in FIG. 2). In this regard, rack assemblies 122, 124, 126 are generally configured for supporting articles within wash chamber 106 while allowing a flow of wash fluid to reach and impinge on those articles, e.g., during a cleaning or rinsing cycle. According to another exemplary embodiment, a silverware basket (not shown) may be removably attached to a rack assembly, e.g., lower rack assembly 122, for placement of silverware, utensils, and the like, that are otherwise too small to be accommodated by rack 122.

Dishwasher 100 further includes a plurality of spray assemblies for urging a flow of water or wash fluid onto the articles placed within wash chamber 106. More specifically, as illustrated in FIG. 2, dishwasher 100 includes a lower spray arm assembly 134 disposed in a lower region 136 of wash chamber 106 and above a sump 138 so as to rotate in relatively close proximity to lower rack assembly 122. Similarly, a mid-level spray arm assembly 140 is located in an upper region of wash chamber 106 and may be located below and in close proximity to middle rack assembly 124. In this regard, mid-level spray arm assembly 140 may generally be configured for urging a flow of wash fluid up through middle rack assembly 124 and upper rack assembly 126. Additionally, an upper spray assembly 142 may be located above upper rack assembly 126 along the vertical direction V. In this manner, upper spray assembly 142 may be configured for urging and/or cascading a flow of wash fluid downward over rack assemblies 122, 124, and 126. As further illustrated in FIG. 2, upper rack assembly 126 may further define an integral spray manifold 144, which is generally configured for urging a flow of wash fluid substantially upward along the vertical direction V through upper rack assembly 126.

Each spray arm assembly 134, 140, 142, integral spray manifold 144, or other spray device may include an arrangement of discharge ports or orifices for directing wash fluid onto dishes or other articles located in wash chamber 106. The arrangement of the discharge ports, also referred to as jets, apertures, or orifices, may provide a rotational force by virtue of wash fluid flowing through the discharge ports. Alternatively, spray arm assemblies 134, 140, 142 may be motor-driven, or may operate using any other suitable drive mechanism. Spray manifolds and assemblies may also be stationary. The resultant movement of the spray arm assemblies 134, 140, 142 and the spray from fixed manifolds provides coverage of dishes and other dishwasher contents with a washing spray. Other configurations of spray assemblies may be used as well. For example, dishwasher 100 may have additional spray assemblies for cleaning silverware, for scouring casserole dishes, for spraying pots and pans, for cleaning bottles, etc. One skilled in the art will appreciate that the embodiments discussed herein are used for the purpose of explanation only, and are not limitations of the present subject matter.

The various spray assemblies and manifolds described herein may be part of a fluid distribution system or fluid circulation assembly 150 for circulating water and wash fluid in the tub 104. More specifically, fluid circulation assembly 150 includes a pump assembly 200 for circulating water and wash fluid (e.g., detergent, water, and/or rinse aid) in the tub 104, as will be described in detail below. Fluid circulation assembly 150 may include one or more fluid conduits or circulation piping for directing water and/or wash fluid from pump assembly 200 to the various spray assemblies and manifolds. For example, as illustrated in FIG. 2, a primary supply conduit 154 may extend from pump assembly 200, along rear 112 of tub 104 along the vertical direction V to supply wash fluid throughout wash chamber 106.

As illustrated, primary supply conduit 154 is used to supply wash fluid to one or more spray assemblies, e.g., to mid-level spray arm assembly 140 and upper spray assembly 142. However, it should be appreciated that according to alternative embodiments, any other suitable plumbing configuration may be used to supply wash fluid throughout the various spray manifolds and assemblies described herein. For example, according to another exemplary embodiment, primary supply conduit 154 could be used to provide wash fluid to mid-level spray arm assembly 140 and a dedicated secondary supply conduit (not shown) could be utilized to provide wash fluid to upper spray assembly 142. Other plumbing configurations may be used for providing wash fluid to the various spray devices and manifolds at any location within dishwasher appliance 100.

The dishwasher 100 is further equipped with a controller 160 to regulate operation of the dishwasher 100. The controller 160 may include one or more memory devices and one or more microprocessors, such as general or special purpose microprocessors operable to execute programming instructions or micro-control code associated with a cleaning cycle. The memory may represent random access memory such as DRAM, or read only memory such as ROM or FLASH. In one embodiment, the processor executes programming instructions stored in memory. The memory may be a separate component from the processor or may be included onboard within the processor. Alternatively, controller 160 may be constructed without using a microprocessor, e.g., using a combination of discrete analog and/or digital logic circuitry (such as switches, amplifiers, integrators, comparators, flip-flops, AND gates, and the like) to perform control functionality instead of relying upon software.

The controller 160 may be positioned in a variety of locations throughout dishwasher 100. In the illustrated embodiment, the controller 160 may be located within a control panel area 162 of door 116 as shown in FIGS. 1 and 2. In such an embodiment, input/output (“I/O”) signals may be routed between the control system and various operational components of dishwasher 100 along wiring harnesses that may be routed through the bottom of door 116. Typically, the controller 160 includes a user interface panel/controls 164 through which a user may select various operational features and modes and monitor progress of the dishwasher 100. In one embodiment, the user interface 164 may represent a general purpose I/O (“GPIO”) device or functional block. In one embodiment, the user interface 164 may include input components, such as one or more of a variety of electrical, mechanical or electro-mechanical input devices including rotary dials, push buttons, and touch pads. The user interface 164 may include a display component, such as a digital or analog display device designed to provide operational feedback to a user. The user interface 164 may be in communication with the controller 160 via one or more signal lines or shared communication busses.

It should be appreciated that the invention is not limited to any particular style, model, or configuration of dishwasher 100. The exemplary embodiment depicted in FIGS. 1 and 2 is for illustrative purposes only. For example, different locations may be provided for user interface 164, different configurations may be provided for rack assemblies 122, 124, 126, different spray arm assemblies 134, 140, 142 and spray manifold configurations may be used, and other differences may be applied while remaining within the scope of the present subject matter.

Referring now generally to FIGS. 3 and 4, a pump assembly 200 will be described according to an exemplary embodiment of the present subject matter. According to the illustrated embodiment, pump assembly 200 is positioned within sump 138 of dishwasher appliance 100 for providing a flow of wash fluid as part of fluid circulation assembly 150. However, it should be appreciated that aspects of the present subject matter may be used to circulate fluid in any suitable appliance.

As shown, pump assembly 200 generally defines an axial direction A, a radial direction R, and a circumferential direction C. According to the illustrated embodiment, pump assembly 200 is positioned entirely within sump 138 and is vertically oriented, e.g., such that the axial direction A is substantially parallel to the vertical direction V of dishwasher appliance 100. However, it should be appreciated that according to alternative embodiments, other coordinate systems may be used to describe pump assembly 200 which may be placed in different orientations and/or at different locations within dishwasher appliance 100.

Referring now specifically to FIG. 3, pump assembly 200 may include a sump housing 202 that generally defines a sump 204 for collecting wash fluid (e.g., flowing as identified by flow arrows 206 during a wash or rinse cycle of dishwasher 100). In this regard, sump housing 202 may be equivalent to sump housing 138 as illustrated in FIG. 2. Sump 204 may further be broken up or divided into a recirculation chamber 220 and a soil collection chamber 222. Between recirculation chamber 220 and soil collection chamber 222, sump 204 may further define a rotor housing 224 which is generally configured for receiving a wet rotor assembly, as described in more detail below. During normal operation of dishwasher 100, each of recirculation chamber 220, soil collection chamber 222, and rotor housing 224 are submerged under water or wash fluid. In this regard, for example, a wash fluid fill level under normal wash or rinse operation is indicated generally by reference numeral 226.

According to the illustrated embodiment, sump housing 202 may define a conical wall 230 that feeds or directs all wash fluid 206 into and toward a bottom of sump 204, e.g., under the force of gravity and/or pumping action of pump assembly 200 as described in more detail below. Dishwasher 100 may further include a wash pump housing 232 that is supported on sump housing 202 by a plurality of circumferentially spaced support legs 234. Wash pump housing 232 may further define an inlet 236 that generally faces down along the vertical direction V for drawing in wash fluid 206 from recirculation chamber 220 during a wash cycle. As illustrated, recirculation chamber 220 may generally be defined as being bounded on the top by wash tub housing 232, on the sides by support legs 234, and on the bottom by rotor housing 224 (or a top of a rotor assembly, as described below). As illustrated in FIG. 3, during a wash cycle, wash fluid 206 is generally drawn into recirculation chamber 220 of sump 204 and directly into inlet 236 of wash pump housing 232.

More specifically, dishwasher 100 may include a wash pump impeller 240 that is positioned within a volute 242 defined by wash pump housing 232. Wash pump impeller 240 may be coupled to a drive shaft 244 which extends substantially along the vertical direction V and is rotatably supported by a top bearing 246 positioned at a top of wash pump housing 232 and a bottom bearing 248 positioned at a bottom 250 of sump housing 202. Drive shaft 244 generally defines an axial direction A and a radial direction R that extends perpendicular to the axial direction A. As described in more detail below, drive shaft 244 may be selectively driven by a motor assembly 270. Thus, during operation, wash pump impeller 240 may be selectively rotated to draw wash fluid 206 from recirculation chamber 220 into volute 242 via inlet 236.

According to the illustrated embodiment, recirculation chamber 220 is generally positioned above and in fluid communication with rotor housing 224, while rotor housing 224 is generally positioned above and in fluid communication with soil collection chamber 222. In this manner, conical wall 230 of sump housing 202 may generally direct wash fluid into recirculation chamber 220. As explained above, if dishwasher 100 is implementing a wash cycle, wash fluid 206 is drawn directly from recirculation chamber 220, passes through wash pump housing 232, and is discharged throughout wash chamber 106, e.g., by diverter assembly 252 or other components of fluid circulation system 150.

Specifically, a diverter assembly 252 may be configured for selectively directing wash fluid 206 within wash chamber 106. More specifically, referring generally to FIGS. 2 and 3, during the wash cycle, wash pump impeller 240 draws wash fluid 206 in from sump 204 (e.g., from recirculation chamber 220) and pumps it to diverter assembly 252. According to an exemplary embodiment, diverter assembly 252 may include a diverter disk (not shown) disposed within a diverter chamber for selectively distributing the wash fluid to various spray assemblies 134, 140, 142, 144 and/or other spray manifolds or devices. For example, the diverter disk may have a plurality of apertures that are configured to align with one or more outlet ports at the top of the diverter chamber, e.g., as defined by a diverter cap. In this manner, the diverter disk may be selectively rotated to provide wash fluid to the desired spray device.

In general, the diverter chamber is positioned above wash pump housing 232 and is fluidly coupled with volute 242 through a supply conduit 264. According to an exemplary embodiment, diverter assembly 252 uses a hydraulically actuated rotation mechanism to position the diverter disk to provide the desired fluid flow between spray assemblies without the need for a motor. However, according to alternative embodiments, the diverter disk could instead be motor driven or may be positioned using any suitable device or apparatus for rotating the diverter disk about the axial direction A.

Referring again to FIG. 3, dishwasher includes motor assembly 270, which is generally configured for rotating wash pump impeller 240, e.g., by driving drive shaft 244. Specifically, as illustrated, motor assembly 270 includes a rotor assembly 272 that is rotatably mounted within rotor housing 224. In this regard, rotor assembly 272 is configured as a “wet” rotor in that it is submerged within wash fluid 206 in a bottom of sump 204. As shown, rotor assembly 272 generally defines a bottom of recirculation chamber 220 and a top of soil collection chamber 222. In addition, motor assembly 270 includes a stator assembly 274 that is positioned around rotor housing 224 outside of sump 204 for selectively rotating rotor assembly 272. In this regard, stator assembly 274 is a “dry” stator assembly 274 and is separated by wash fluid 206 by sump housing 202.

According to an exemplary embodiment, rotor assembly 272 includes an annular rotor magnet 276 and stator assembly 274 includes a plurality of stator conductors 278 that are spaced apart around annular rotor magnet 276 outside of sump housing 202. Annular rotor magnet 276 is configured to generate a rotor magnetic field and stator conductors 278 are configured to generate a stator magnetic field. The rotor magnetic field and the stator magnetic field interact to generate a torque that rotates annular rotor magnet 276 and drive shaft 244, as will be described in more detail below.

Although annular rotor magnet 276 and stator conductors 278 are referred to generally herein as “magnets,” it should be appreciated that these magnets may be any suitable magnetic material, and may be permanent magnets, electromagnets, etc. For example, according to the illustrated embodiment, annular rotor magnet 276 is a permanent magnet and stator conductors 278 are ferromagnetic material with conductive windings, but alternative embodiments may use any suitable combination of annular rotor magnet 276 and stator conductors 278 to generate a torque on drive shaft 244. In addition, stator assembly 274 may have concentrated windings, distributed windings, or any other suitable stator winding configuration. Furthermore, annular rotor magnet 276 and stator conductors 278 may include any suitable coating or covering, such as a metallic or non-metallic magnetic shielding material or retaining structure.

During operation, a controller (e.g., a dedicated motor controller or an appliance controller such as controller 160) may control the speed and direction of rotation of rotor assembly 272 and the rotation of drive shaft 244 by selectively applying electric current to stator assembly 274 to cause rotor assembly 272 and drive shaft 244 to rotate. Although motor assembly 270 is illustrated herein as a brushless DC motor, it should be appreciated that any suitable motor may be used while remaining within the scope of the present subject matter. For example, according to alternative embodiments, motor assembly 270 may instead be a stepper motor, a synchronous permanent magnet motor, an AC motor, or any other suitable type of motor in any suitable configuration.

Referring now generally to FIGS. 3 and 4, rotor assembly 272 will be described in more detail according to an exemplary embodiment of the present subject matter. Specifically, FIG. 3 illustrates a cross-section of rotor assembly 272 positioned within pump assembly 200 and FIG. 4 provides a perspective view of rotor assembly 272 with annular rotor magnet 276 removed for clarity. As shown, rotor assembly 272 includes a central hub 280 that is coupled to drive shaft 244. Annular rotor magnet 276 is positioned concentrically around central hub 280 such that an annular flow path 282 is defined between central hub 280 and annular rotor magnet 276. In this regard, wash fluid 206 may flow between recirculation chamber 220 and soil collection chamber 222 through rotor housing 224 and rotor assembly 272 (e.g., via flow path 282).

In addition, rotor assembly 272 includes a plurality of helical vanes 284 that extend between central hub 280 and annular rotor magnet 276. In this regard, helical vanes 284 extend substantially along the radial direction and rigidly join central hub 280 to annular rotor magnet 276. Thus, as stator assembly 274 drives annular rotor magnet 276, torque is transferred to central hub 280 and drive shaft 244 via helical vanes 284. According to the illustrated embodiment, rotor assembly 272 includes three helical vanes 284, although it should be appreciated that any other suitable number, size, position, and configuration of vanes 284 may be used while remaining within the scope of the present subject matter.

According to an exemplary embodiment, each vane 284 may extend from a top to bottom of central hub 282 and may wrap around approximately one third of the circumference of central hub 280 and annular rotor magnet 276. In this regard, contains 284 may be large, flat, and helical, thereby covering a large area to help restrict undesirable flow of sediment or soil through flow path 282. For example, vanes 284 may define a void ratio that is equal to a surface area covered by vanes 284 within a single cross-section taken perpendicular to the axial direction A over the total cross-sectional area of flow path 282. Notably, due to the large sweeping design of vanes 284, the void ratio may be small, such as less than 20%, less than 10%, less than 5% or lower.

Referring again to FIG. 3, pump assembly 200 may include a discharge conduit 290 that is fluidly coupled to soil collection chamber 222. In this regard, during a drain or discharge cycle of dishwasher 100, rotor assembly 272 may reverse direction and vanes 284 may drive wash fluid 206 down into soil collection chamber 222 and out of discharge conduit 290. Although only vanes 284 are illustrated as being used to perform a drain cycle, it should be appreciated that according to alternative embodiments, an additional drain impeller may be mounted to drive shaft 244 within soil collection chamber 222. According to such an embodiment, for example, vanes 284 may be removed altogether and may be replaced by spokes that are intended only to structurally couple annular rotor magnet 276 to central hub 280. Other drain configurations are possible and within the scope of the present subject matter.

In order to prevent inadvertently drawing wash fluid 206 into soil collection chamber 222 from drain conduit 290, pump assembly 200 may further include a check valve 292 that is operably coupled to discharge conduit 290 to prevent the flow of wash fluid 206 through discharge conduit 290 back into sump 204. Thus, during operation of dishwasher 100, motor assembly 270 may alternate between a wash cycle and a drain cycle. During the wash cycle (as indicated by solid flow arrows 206 in FIG. 3), stator assembly 274 rotates rotor assembly 272 in a first direction (e.g., the counterclockwise direction) such that wash pump impeller 240 draws wash fluid 206 in through inlet 236 and circulates wash fluid 206 through wash chamber 106. Notably, check valve 292 remains closed to prevent wash fluid 206 and collected soil from soil collection chamber 222 from passing through flow path 282 into recirculation chamber 220. By contrast, during a drain cycle (as indicated by dotted flow arrows 206 in FIG. 3), stator assembly 274 may rotate rotor assembly 272 in the opposite direction (e.g., clockwise direction) such that helical vanes 284 of rotor assembly 272 urge wash fluid 206 downward through soil collection chamber 222, through discharge conduit 290, and past the forward biased check valve 292 to an external drain.

It should be appreciated that pump assembly 200 is described herein only for the purpose of explaining aspects of the present subject matter. Modifications and variations may be made to pump assembly 200 while remaining within the scope of the present subject matter. For example, the size, geometry, and relative positioning of rotor assembly 272 and stator assembly 274 may adjusted while remaining within the scope of the present subject matter. In addition, the angle, number, and configuration of vanes 284 may vary. Pump assembly 200 as described above provides a simple, compact, and effective system for urging a flow of wash fluid 206 within fluid circulation assembly 150 or any other pump system within dishwasher appliance 100. Other configurations and benefits will be apparent to those of skill in the art.

This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they include structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims. 

What is claimed is:
 1. A dishwasher appliance defining a vertical direction, the dishwasher appliance comprising: a wash tub that defines a wash chamber; a sump housing defining a sump for collecting wash fluid, the sump defining a recirculation chamber, a soil collection chamber, and a rotor housing positioned between the recirculation chamber and the soil collection chamber; a rotor assembly rotatably mounted within the rotor housing; and a stator assembly positioned around the rotor housing outside of the sump for selectively rotating the rotor assembly.
 2. The dishwasher appliance of claim 1, further comprising: a drive shaft defining an axial direction and a radial direction perpendicular to the axial direction; a top bearing mounted within a wash pump housing; and a bottom bearing mounted at a bottom of the sump housing.
 3. The dishwasher appliance of claim 2, wherein the rotor assembly comprises: a central hub coupled to the drive shaft; an annular rotor magnet positioned concentrically around the central hub and defining a flow path through the rotor housing between the recirculation chamber and the soil collection chamber; and a plurality of helical vanes that extend between the central hub and the annular rotor magnet.
 4. The dishwasher appliance of claim 3, wherein the plurality of helical vanes is three vanes.
 5. The dishwasher appliance of claim 3, the plurality of helical vanes within the flow path defines a void radio of less than 10 percent.
 6. The dishwasher appliance of claim 2, wherein the stator assembly is operable to rotate the drive shaft in a first direction during a wash cycle and in a second direction during a drain cycle, the second direction being opposite the first direction.
 7. The dishwasher appliance of claim 2, wherein the drive shaft extends parallel to the vertical direction defined by the dishwasher appliance.
 8. The dishwasher appliance of claim 1, further comprising: a wash pump housing defining an inlet; and a wash pump impeller positioned within the wash pump housing and being coupled to a drive shaft for drawing wash fluid through the inlet from the recirculation chamber.
 9. The dishwasher appliance of claim 8, wherein the inlet faces down along the vertical direction.
 10. The dishwasher appliance of claim 1, wherein the soil collection chamber is positioned below the rotor assembly and the recirculation chamber is positioned above the rotor assembly.
 11. The dishwasher appliance of claim 1, further comprising: a discharge conduit fluidly coupled to the soil collection chamber.
 12. The dishwasher appliance of claim 11, further comprising: a check valve operably coupled to the discharge conduit to prevent a flow of wash fluid through the discharge conduit into the soil collection chamber.
 13. A pump assembly for a dishwashing appliance, the dishwashing appliance comprising a sump housing defining a sump for collecting wash fluid, the sump defining a recirculation chamber, a soil collection chamber, and a rotor housing positioned between the recirculation chamber and the soil collection chamber, the pump assembly comprising: a drive shaft defining an axial direction and a radial direction perpendicular to the axial direction; a rotor assembly coupled to the drive shaft and being rotatably mounted within the rotor housing; and a stator assembly positioned around the rotor housing outside of the sump for selectively rotating the rotor assembly.
 14. The pump assembly of claim 13, wherein the rotor assembly comprises: a central hub coupled to the drive shaft; an annular rotor magnet positioned concentrically around the central hub and defining a flow path through the rotor housing between the recirculation chamber and the soil collection chamber; and a plurality of helical vanes that extend between the central hub and the annular rotor magnet.
 15. The pump assembly of claim 14, wherein the plurality of helical vanes is three vanes.
 16. The pump assembly of claim 14, the plurality of helical vanes within the flow path defines a void radio of less than 10 percent.
 17. The pump assembly of claim 13, further comprising: a wash pump housing defining an inlet facing down along a vertical direction; and a wash pump impeller positioned within the wash pump housing and being coupled to the drive shaft for drawing wash fluid through the inlet from the recirculation chamber.
 18. The pump assembly of claim 13, wherein the soil collection chamber is positioned below the rotor assembly and the recirculation chamber is positioned above the rotor assembly.
 19. The pump assembly of claim 13, further comprising: a discharge conduit fluidly coupled to the soil collection chamber.
 20. The pump assembly of claim 19, further comprising: a check valve operably coupled to the discharge conduit to prevent a flow of wash fluid through the discharge conduit into the soil collection chamber. 